[RUBY] rails [Procedure for displaying an error statement when data transmission fails due to create action]

1. Write the error statement in the view file you want to display. This time, write it in new.html.erb. 〇〇 is named by yourself.

<%= render '〇〇/error_messages', model: f.object   %> 

2.〇〇/_error_messages.html.erb Create and describe a file.

#〇〇/_error_messages.html.Contents of erb
<%if variable A.errors.any? %>
  <div id="error_explanation">
    <ul>
      <%Variable A.errors.full_messages.each do |message| %>
      <li class="error-alert"><%= message %></li>
      <% end %>
    </ul>
  </div>
<% end %>

3. If the data can be saved, the screen transitions to the index action of the same controller (items controller this time), and if it cannot be saved, the items # new action is displayed.

def create
    @item= Item.new(item_params)
     if @item.save
      redirect_to action: 'index'
    else
      render :new
    end
  end

4. If data transmission fails with this new.html.erb <%= render '〇〇/error_messages', model: f.object %> An error statement will be displayed in the place where